JP3104310B2 - Fluororesin coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluororesin coating, and more particularly, to a fluororesin coating colored chromatically by a pigment-coated mica, without impairing post-processing durability after coating, thereby improving color development. It relates to an improved fluororesin coating.

[0002]

2. Description of the Related Art Fluorine resins have excellent non-adhesiveness and chemical resistance, so that they can be used in frying pans, pans, hot plates,
It is used in a wide range of applications such as kitchen equipment such as inner pots for jar rice cookers, food containers, electric products, food industry, and electric and mechanical industries.

[0003] Conventionally, these fluororesin coatings are mainly colorless and transparent, in which the color of the undercoat can be seen through as they are, or monotones such as white, gray, black, etc., and at most, only metallic tones having a metallic luster can be obtained. I didn't. However, in recent years, the need for color has been increasing, especially for general products such as household goods, and refrigerators that can order colors have been released. It has become.

[0004]

[Application to be solved by the invention] Therefore, the present inventors
By using pigment-coated mica as a pigment, it has been found that a better color than ever before can be obtained.
No. 301169, Japanese Patent Application No. 01-326682, and Japanese Patent Application No. 02-4697. However, in these inventions, there is a problem that, although a pale and beautiful coloration can be obtained, a color with strong saturation cannot be obtained.

As a method of obtaining a highly saturated color using such pigment-coated mica, a method of mixing carbon black or the like with this or a method of darkening the base is known. The problem is the loss of color transparency.

As a method for darkening the base, there is a means using a dark primer. However, an adhesion aid compounded to obtain an adhesive function required for the primer, for example, PAI
(Polyamide imide) and the like significantly reduce the elongation at break of the coating film. Therefore, when the coating material is coated and then molded, there is a problem that cracks are generated in the coating film and whitening occurs.

On the other hand, when no adhesive aid such as PAI is used,
Cannot bond to substrate. For example, if a base layer containing only carbon and fluorine resin is provided on a base material provided with fine irregularities and adhesion is attempted only by the anchoring effect, the adhesion is reduced by carbon, and practical adhesion cannot be obtained.

In view of the above, the invention of the present application provides a fluororesin coating having improved color development without impairing post-processing durability after coating the fluorinated resin coating colored chromatically with pigment-coated mica. It is to try. This application includes two inventions.

[0009]

According to a first aspect of the present invention, there is provided a fluororesin coating on which a darkly colored fluororesin layer is laminated on a substrate provided with fine irregularities, and a coating is formed thereon. The pigment to be coated is an inorganic pigment, and the inorganic pigment is a) to d) a) a transparent inorganic pigment, and the optical thickness to be coated (optical thickness = geometric thickness × refractive index) Is 0.2 μ or more.
B) an opaque inorganic pigment, c) a mixture of a transparent inorganic pigment and an opaque inorganic pigment, d) a laminate of a transparent inorganic pigment and an opaque inorganic pigment. Wherein a fluorine resin layer containing pigment-coated mica is laminated.

[0010] Embodiments of the first invention of the present application include at least the following. (A) The fluororesin coating of the first invention, wherein a fluororesin layer substantially free of pigments and heat-resistant polymers is laminated on the outermost layer. (B) The fluororesin layer, which is colored dark, has a solid content of 0.
The fluororesin coating according to the first aspect of the present invention, which contains 5% by weight or more and 5% by weight or less of carbon black.

(C) The fluororesin layer colored darkly is
The fluororesin coating according to the first aspect of the present invention, comprising a heat-resistant polymer in an amount of 0.5% by weight or more and 10% by weight or less in a solid content. (D) The fluorine resin according to the first aspect of the present invention, wherein the fluorine resin in the darkly colored fluorine resin layer is composed of 2% by weight or more and 12% by weight or less of a hot-melt fluorine resin and 98% by weight or less and 88% by weight or more of PTFE. Resin coating.

(E) The fluororesin coating according to the first aspect of the present invention, wherein the darkly colored fluororesin layer contains 1% by weight to 10% by weight of solids other than the fluororesin.

(F) the opaque inorganic pigment is iron oxide;
The fluororesin coating according to the first aspect, wherein the transparent inorganic pigment is titanium oxide.

The fluororesin coating of the second invention of the present application is provided with a dark layer on a substrate provided with fine irregularities without erasing the irregularities along the irregularities. The pigment to be coated is an inorganic pigment, and the inorganic pigment is
a) to d) a) A transparent inorganic pigment having an optical thickness to be coated (optical thickness = geometric thickness × refractive index) of at least 0.2 μm.
B) an opaque inorganic pigment, c) a mixture of a transparent inorganic pigment and an opaque inorganic pigment, d) a laminate of a transparent inorganic pigment and an opaque inorganic pigment. Wherein a fluorine resin layer containing pigment-coated mica is laminated.

The above-described second embodiment of the present invention includes at least the following. (A ') The fluororesin coating of the second invention, wherein the substrate is made of aluminum or an aluminum alloy, and the dark layer is an anodic oxide film. (B ′) The fluororesin coating according to the above (a ′), wherein the dark color layer is a dark color layer formed by electrolytic coloring of an anodic oxide film.

(C) The fluororesin coating according to the above (a), wherein the dark layer is a dark layer in which a pigment is deposited in pores or the like of an anodized film. (D ') The fluororesin coating according to the second invention, wherein the fluororesin comprises 2 wt% to 12 wt% of a hot-melt fluororesin and 98 wt% to 88 wt% of polytetrafluoroethylene (PTFE). .

[0017]

[Functions] (Common items of the first and second inventions of the present application) The substrates to which the first and second inventions of the present application can be applied include metals such as aluminum, aluminum alloys, iron and stainless steel, glass, ceramics and the like. No matter what you use,
The effect of the present invention is particularly great for a metal substrate that can be post-processed after coating. Further, in the second invention, aluminum or an aluminum alloy is most preferably used from the viewpoint that a dark color layer is easily formed.

The fine irregularities of the substrate described in the first and second aspects of the present invention are not irregularities caused by physical roughening of a metal surface or the like usually performed by sand blasting, grid blasting or the like. Although it does not matter, it mainly means unevenness due to etching performed chemically, electrochemically, or a combination thereof. Microscopically, spongy or metallic crystal grains partially dissolve and form complicated irregularities.

However, the processing method is not limited to chemical or electrochemical etching, etc.
A rough surface capable of obtaining a peel strength of about 2 kg / cm in a combination of the irregularities and the coating of only PTFE can be applied to the first and second inventions of the present application.

In the case of sand blast, grid blast or the like alone, 2 kg
/ Cm. In addition, since such irregularities are easily obtained by electrochemically etching aluminum or an aluminum alloy, such materials and methods are particularly preferably used.

Examples of the fluorine resin used in the first and second aspects of the present invention include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoro. Alkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (P
CTFE) or ethylene-chlorotrifluoroethylene copolymer (ECTFE).

The fluororesin is not only a resin powder but also an aqueous dispersion of a fluororesin obtained by an emulsion polymerization method, a dispersion of a fluororesin powder dispersed in an aqueous medium, an organosol of a fluororesin, or an emulsion of an organosol in water. Etc. can be used in any form. It is particularly preferably used in the form of an aqueous dispersion.

The particle size and blending amount of the pigment-coated mica used in the first and second inventions of the present application can be appropriately determined in consideration of the coloring properties, abrasion resistance, the degree of occurrence of defects, and the like. 5 μm or more and 200 μm or less, particularly preferably 5 μm or more and 100 μm or less are used. The compounding amount is preferably 1% by weight or more and 10% by weight or less in the solid content, and particularly preferably 2% by weight or more and 7% by weight or less.

The inorganic pigment coated on the mica is not particularly limited, but typically, carbon black, iron hydroxide, iron oxide, ferrocyanide, chromium hydroxide, chromium oxide,
Titanium oxide and the like can be mentioned. In the case of coating with a transparent inorganic pigment represented by titanium oxide, the optical thickness (optical thickness = geometric thickness × refractive index) is set to 0. It is preferable to be 2 μm or more and 0.4 μm or less. On the other hand, when the inorganic pigment coated on the mica is opaque like iron oxide, the thickness is not particularly limited.

The coating of the inorganic pigment may be performed by mixing or laminating transparent and opaque inorganic pigments, and various colors can be obtained depending on the combination of types and thicknesses. There are many types of mica used here depending on the contained components, and a typical mica composition formula is muscovite (muscovite) K ₂ Al ₄ (Si ₃ Al) ₂ O
₂₀ (OH) ₄ , phlogovite (phlogopite) K ₂ Mg ₆
(Si ₃ Al) ₂ O ₂₀ (OH) ₄ , biotite (biotite) K ₂ (MgFe ²⁺ ) ₆ (Si ₃ Al) ₂ O
₂₀ (OH) ₄ or the like, and any of them may be used.

(Items Regarding the First Invention of the Present Application) As a coloring method used for the dark-colored fluororesin layer of the first invention of the present application, a method of blending an inorganic pigment is used.
As such an inorganic pigment, carbon black is mainly preferably used, but is not particularly limited as long as it can be colored in a dark color such as black, dark blue or black brown, and various kinds of pigments may be mixed and used.

Although the thickness of the dark-colored fluororesin layer of the first invention of the present application is not particularly limited as long as the dark color can be obtained, the thickness is preferably 5 μm or more and 30 μm or less. The thickness of the fluororesin layer containing the pigment-coated mica is also not particularly limited, but is preferably laminated to 5 μm or more and 30 μm or less.

The fluororesin layer which does not substantially contain a pigment or a heat-resistant polymer, which is coated on the outermost layer, is also preferably 5 as described above.
It is laminated to a thickness of not less than μ and not more than 30 μ. As the fluorine resin used for this layer, the above-mentioned fluorine resin is used. Further, these fluorine resins may be mixed and used at an arbitrary ratio.

As described above, carbon black is preferably used as the pigment used for the darkly colored fluorine resin layer, because a small amount of carbon black enables coloring with strong hiding power. Nevertheless, the incorporation of pigments reduces the adhesion between the coating and the substrate and also reduces the elongation of the coating, so the amount should be kept to a minimum that does not reduce their physical properties as long as they can be colored. The content must be 0.5% by weight or more and 5% by weight or less. In particular, it is preferably from 1% by weight to 3% by weight.

In order to bond such a fluororesin layer in the usual manner, that is, by blending an adhesion aid, the adhesion aid is generally blended in an amount of about 25% of the solid content. The elongation is significantly lost. Therefore, by combining with the fine irregularities of the base material, the amount of the adhesive aid can be reduced, and as a result, sufficient adhesive strength can be obtained while maintaining the elongation of the coating film within the range that can be post-processed. I found it. Adhesion aids to be blended here are heat-resistant polymers,
For example, polyamide imide, polyether sulfone, polyphenylene sulfide, and the like are typically given. The compounding amount is 0.5% by weight or more and 10% by weight for the purpose of obtaining a sufficient adhesive force by combination with the unevenness of the base material, and the elongation of the coating film within a range that can be post-processed. It is preferable to set the following. Particularly preferably, 1% by weight or more and 5% by weight or more.
% By weight or less.

The amount of solids other than the fluororesin in the darkly colored fluororesin layer, that is, the total solids of the pigment and the adhesion promoter is 10% by weight or less, preferably 8% by weight, from the viewpoint of maintaining the elongation of the coating film. The content is not more than 1% by weight and preferably not less than 2% by weight from the viewpoint of coloring and adhesion.

As a method for obtaining an adhesive force without reducing the elongation of a coating film without using the above-mentioned heat-resistant polymer, a composition of a fluorine resin having a composition of 2% by weight to 12% by weight is used. And 98% by weight or less and 88% by weight or more of PTFE
And a combination with fine irregularities was found. Also in this case, the compounding amount of carbon is preferably 0.5% by weight or more and 5% by weight or less, particularly preferably 1% by weight or more and 3% by weight or less in the solid content.

The hot-melt fluororesin used here is P
FA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), ETFE
(Tetrafluoroethylene-ethylene copolymer), CT
Polymers and copolymers such as FE (polychlorotrifluoroethylene) are used.

When PTFE is at 340 ° C. to 380 ° C., 1
It is a non-melting material generally referred to as having a high viscosity of 0 ¹¹ to 10 ¹³ poise, whereas the hot-melt fluororesin mixed with this is PFA (10 ⁴ to 10 ^{5 at} 380 ° C.), F
EP (4 × 10 ⁴ to 10 ^{5 at} 380 ° C.), ETF
E (10 ⁴ to 10 ^{5 at} 300 to 330 ° C.), CT
The point is that the melt viscosity is as extremely low as FE (10 ^{7 at} 230 ° C.), and the material is not limited to these as long as it is a heat-meltable fluorine resin.

Although the mechanism for improving the adhesive strength by the addition of the hot-melt fluororesin has not been clarified yet,
(1) The anchoring effect is increased because of low melt viscosity, which makes it easy to enter fine irregularities. (2) It is presumed to be a combined effect such as the decomposition product being chemically bonded to the metal surface when the coating film is sintered.

In the present invention, 1. Fine irregularities,
2. 2. heat-resistant polymer; It is also possible to use a combination of the three techniques of a fluorine resin mixed with a hot-melt fluorine resin / PTFE.

(Items Regarding the Second Invention of the Present Application) In the second invention of the present application, as a method of providing a dark layer along the unevenness of the substrate or without erasing the unevenness, a dark colored pigment is blasted. Sandblasting by attaching to sand and physically fitting and adhering to the substrate, deposition of dark pigment in solution, and electrolytic coloring with the substrate limited to metal are all methods. Applicable. As a particularly preferable method, there is a method in which the substrate is made of aluminum or an aluminum alloy, and an anodic oxide film formed after providing fine irregularities is a dark layer. First, there is a method in which a dark pigment is deposited in a solution state into fine pores of a porous anodic oxide coating or introduced by electrophoresis or the like to deposit. In any case, it is preferable in view of stability to seal after the deposition. The second is a method in which an alternating current is applied in a metal salt bath after the formation of the anodic oxide film to perform an alternating current electrolytic coloring. The reason why the dark layer is provided along the unevenness of the substrate or without eliminating the unevenness is to adhere the fluorine resin layer to the substrate.

As described above, a method of laminating a fluororesin containing mica on a substrate colored in a dark color and compounding an adhesion aid such as polyamideimide or polyethersulfone in order to obtain strong adhesion is known. Generally, these adhesion aids are originally brown, so that they mix with the color of mica and cause a problem of blemishes. Therefore, it is preferable that the composition of the fluorine resin be 2% by weight or more and 12% by weight or less. A method is used in which a mixture of a hot-melt fluororesin and 98% by weight or more and 88% by weight or more of PTFE is combined with fine irregularities.

The hot-melt fluororesin used here is the first resin.
These are the same as those described in the invention of the above. The mechanism for improving the adhesive strength by the addition of the hot-melt fluorine resin is the same as that described in the first invention.

The outermost layer may be coated with a fluororesin layer substantially free of pigments or heat-resistant polymers.
It is laminated to a thickness of 30 μm or less. As the fluorine resin used for this layer, the above-mentioned fluorine resin is used. Further, these fluorine resins may be mixed and used at an arbitrary ratio.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of the first invention of the present application will be described below. Examples 1 to 3 and Comparative Examples 1 to 3 Aluminum materials having a thickness of 2.5 mm (ASB material manufactured by Kobe Steel Ltd.) were used. First, using this as an anode, electrochemical and etching treatments were performed in an aqueous solution of ammonium chloride with an amount of electricity of 25 clones / cm ² to form fine irregularities on the surface. (However, in Comparative Example 2, only the surface roughening treatment by sandblasting was performed.)

This surface was coated with a resin composition shown in Table 1 as a first layer, dried and baked at 420 ° C. for 10 minutes. Thereafter, a resin having the resin composition shown in Table 1 was further coated as a second layer, dried, and baked at 420 ° C. for 10 minutes. The condition for forming the third layer (outermost layer) is as follows (only in Examples 2 and 3), a PTFE diversion (D-1F manufactured by Daikin Industries, Ltd.) containing no filler is coated. And after drying the water 420
Bake at ℃ for 10 minutes. The resin thickness of this is 1st layer, 2nd layer
Each layer was coated with 15 μm to give a total of 30 μm.
When the third layer is laminated, its thickness is set to 10 μm, and a total of 40
μ.

The coated plate thus obtained was deep drawn by press molding to obtain a rice cooker. The following items were carried out as evaluation methods for the coated plate pressed product thus obtained. The evaluation results are also shown in Table 1.

The evaluation method is as follows: Adhesion: (%) A grid (1 mm)
Insert 100 squares), apply cellophane tape to this surface, and immediately peel off. Repeat this 20 times 10
The remaining number of the squares is determined as the adhesion rate (%) (both bottom and side surfaces were evaluated).

Peel strength: (kg / cm) A fluororesin tape was heat-sealed to the coated surface,
Peeling is performed in the direction of 0 °, and the force required for peeling per 1 cm width is defined as the peel strength.

Pinhole degree: (mA) A pot-shaped molded product is filled with a 2% by weight aqueous NaCl solution, one electrode is placed in the solution, and the other is attached to the outer wall of the molded product, and the amount of current (mA) is measured. . If the total area of the pinholes reaching the substrate (in this embodiment, the aluminum alloy) is large, the amount of current is increased, and this is an index of the number of pinholes. The higher the pinhole degree, the lower the corrosion resistance, which is not preferable.

Whitening during color tone press: Judgment by visual observation.

[0048]

[Table 1]

Next, an embodiment of the second invention of the present application will be described.
An aluminum material having a thickness of 2.5 mm (ASB material manufactured by Kobe Steel Co., Ltd.) was used. First, using this as an anode, an electrochemical and etching treatment was performed with an amount of electricity of 25 coulomb / cm ^{2 in} an aqueous solution of ammonium chloride to form fine irregularities on the surface.

An anodic oxide film was formed on the surface by applying a DC voltage of 15 V for 1 minute at room temperature in dilute sulfuric acid.
Subsequently _{H 2 SO 4 7g / l,} CuSO 4 20g /
A 20 V AC was applied in a bath of 1 l to perform black AC electrolytic coloring for about 10 minutes. On top of this, PTFE 36.8
5.% by weight, 3.2% by weight of PFA, 3% by weight of colored mica (Iriodin 235 manufactured by Merck Japan), surfactant 6.
A dispersion consisting of 4% by weight and 50.6% by weight of water is applied and dried, and then baked at 400 ° C. for 30 minutes to obtain a coating of about 30 minutes.
μ was obtained.

The coating plate thus obtained had a coating film having a vivid green metallic luster. Using this plate, a rice cooker inner pot was prepared. No peeling of the coating film was observed by press molding, and no whitening due to defect formation was observed.

[0052]

According to the present invention, the coloring property is improved without impairing the post-processing durability after coating the fluorinated resin coating colored chromatically by the pigment-coated mica. Particularly, it is suitably used for a fluororesin-coated product in which it is desired that the color saturation is remarkably high. Documents describing chemical formulas, etc.

Continuation of front page (56) References JP-A-56-18825 (JP, A) JP-A-56-18824 (JP, A) JP-A-54-33551 (JP, A) JP-A-2-251440 (JP) JP-A-53-1145 (JP, A) JP-A-63-200868 (JP, A) JP-A-48-55072 (JP, A) Japanese Utility Model Showa 62-9524 (JP, U) 43-25644 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 B05D 1/00-7/26 A47J 27/00-29/06 A47J 33 / 00-36/42

Claims (12)

(57) [Claims] 1. A dark-colored fluororesin layer is laminated on a substrate provided with fine irregularities, and a pigment to be coated thereon is an inorganic pigment. d) a) A transparent inorganic pigment having an optical thickness to be coated (optical thickness = geometric thickness × refractive index) of 0.2 μm or more.
B) an opaque inorganic pigment, c) a mixture of a transparent inorganic pigment and an opaque inorganic pigment, and d) a laminate of a transparent inorganic pigment and an opaque inorganic pigment. A fluororesin layer containing the pigment-coated mica according to claim 1. 2. The fluororesin coating according to claim 1, wherein a fluororesin layer substantially containing no pigment or heat-resistant polymer is laminated on the outermost layer. 3. The fluororesin coating according to claim 1, wherein the fluororesin layer colored in a dark color contains carbon black in an amount of 0.5 to 5% by weight based on the solid content. 4. The fluororesin coating according to claim 1, wherein the fluororesin layer colored in a dark color contains 0.5 to 10% by weight of the heat-resistant polymer in the solid content. 5. The dark-colored fluororesin layer, wherein the fluororesin layer comprises 2 wt% to 12 wt% of a hot-melt fluororesin and 98 wt% to 88 wt% of polytetrafluoroethylene (PTFE). The fluororesin coating according to claim 1, comprising: 6. The fluororesin coating according to claim 1, wherein the fluororesin layer colored in a dark color contains a solid content other than the fluororesin of 1% by weight or more and 10% by weight or less. 7. The fluororesin coating according to claim 1, wherein the opaque inorganic pigment is iron oxide and the transparent inorganic pigment is titanium oxide. 8. A dark color layer is provided on a substrate provided with fine irregularities along the irregularities or without eliminating the irregularities, and the pigment to be coated thereon is an inorganic pigment. The pigment is a) to d) a) a transparent inorganic pigment, and the coated optical thickness (optical thickness = geometric thickness × refractive index) is 0.2 μm or more.
B) an opaque inorganic pigment, c) a mixture of a transparent inorganic pigment and an opaque inorganic pigment, d) a laminate of a transparent inorganic pigment and an opaque inorganic pigment. A fluororesin layer containing the pigment-coated mica according to claim 1. 9. The fluororesin coating according to claim 8, wherein the substrate is made of aluminum or an aluminum alloy, and the dark layer is an anodized film. 10. The fluororesin coating according to claim 9, wherein the dark color layer is a dark color layer formed by electrolytic coloring of an anodic oxide film. 11. The fluororesin coating according to claim 9, wherein the dark-color layer is a dark-color layer in which a pigment is deposited on pores or the like of an anodized film. 12. The fluororesin coating according to claim 8, wherein the fluororesin comprises 2 to 12% by weight of a hot-melt fluororesin and 98 to 88% by weight of polytetrafluoroethylene (PTFE). .